In U.S. Pat. Nos. 1,268,235, 2,538,443, and 2,695,754, reinforcements for concrete cross ties are provided at a single level within the cross tie, and are stressed after the concrete is poured in place through the use of mechanical fasteners at either end of the cross tie reinforcement.
In U.S. Pat. No. 1,072,053, a prestressed concrete cross tie reinforcement is provided which varies in its location from a low point below each track member to an upper location in the center portion of the transverse cross tie.
In none of these references is there any recognition of the desirability of locating the reinforcements at the neutral axis of the section to increase the fatigue life.
In U.S. Pat. No. 1,130,081, the concrete reinforcement makes a 90.degree. bend at either end, and the stressing mechanical fasteners are located adjacent the rails.
In U.S. Pat. Nos. 4,108,377 and 4,150,790, reinforcements for concrete cross ties are provided which are vertically spaced and which are prestressed before the concrete is poured.
However, neither of these constructions have the reinforcements located at the neutral axis of the section or is there any realization that locating the reinforcements at the neutral axis of the section will reduce fatigue.
Furthermore, no attempt is made at minimizing concrete and maximizing strength.